Existing systems and methods do not provide information about a mismatch of an identity (e.g., Location Area Identity (LAI)) received in broadcasted system information and an identity received during a registration accept procedure. Thus, behavior of a mobile terminal (e.g., User Equipment (UE) or mobile station) is unpredictable. Further, according to the current specification (or requirements), the mobile terminal should update the LAI value of a Subscriber Identity Module (SIM) with the LAI value received in a Location Area Update (LAU) accept message. However, the current specification does not clearly define how to handle a situation where there is a mismatch in identities values (e.g., LAI values) between the LAU accept message and the broadcasted LAI (e.g., system information block (SIB) information).
If the mobile terminal enters a new location area and receives the LAI value (e.g., LAI-A) in the broadcasted system information, the mobile terminal triggers a LAU request message to a communication network and receives a LAU accept message from the communication network. If the communication network sends different LAI (e.g., LAI-B) in the LAU accept message, the mobile terminal updates the LAI value in the SIM with received LAI value (e.g., LAI-B). After updating the SIM LAI value with the LAI-B value, the mobile terminal will again detect the LAI (e.g., LAI-A) from the broadcasted system information. Further, the mobile terminal detects the LAI change between the LAI value stored in the SIM and the current LAI detected from the broadcasted system information. After detecting the LAI change, the mobile terminal again initiates the LAU procedure. Thus, the LAU procedure can run continuously in a loop, thereby resulting in battery drain in the mobile terminal.
Consider a situation where the mobile terminal is powered ON and a cell search process is completed, and a Non-Access Stratum (NAS) of the mobile terminal receives the LAI-A as the currently camped LAI which is read from the broadcasted system information. In such case, the mobile terminal initiates the LAU procedure and sends the location update request message to the communication network. Based on the location update request message, the communication network sends the LAU accept message with different LAI value (e.g., LAI-B). When the mobile terminal receives the LAU accept message, the mobile terminal updates the LAI value (LAI-A) of SIM with the received LAI value (e.g., LAI-B). Further, a Radio Resource (RR) connection of the mobile terminal is released and the mobile terminal moves to or enters an idle mode. The mobile terminal receives the CELL Index (IND) with LAI-A. Then, the mobile terminal will perform the LAU procedure again of there is a LAI mismatch between the LAI value in the SIM and the broadcasted LAI value. In this case, the mobile terminal can run the LAU procedure repeatedly until the correct LAI value is received in the LAU accept message from the communication network.
Consider another situation where after initial registration procedure is successful on the LAI-A, the mobile terminal is moved to or enters a different location and receives the LAI-B from the broadcasted system information. In such case, the mobile terminal starts the LAU procedure and sends the LAU request to the communication network. The communication network sends the LAU accept message with different LAI value (e.g., LAI-C). When the mobile terminal receives the LAU accept message, the mobile terminal updates the LAI value (e.g., LAI-A) of the SIM with the received LAI value (e.g., LAI-C), and the mobile terminal will remove the LAI-C from a forbidden LAI list, if the LAI-C is present in the forbidden LAI list. After the mobile terminal removes the LAI-C from the forbidden LAI list, the RR connection is released and the mobile terminal moves to or enters the idle mode. If the mobile terminal communicates with the communication network sending the LAI-C and attempts the registration on the forbidden LAI, the mobile terminal receives the rejection message from the communication network.
Consider still another situation where after the initial registration procedure is successful on a Public Land Mobile Communication network-1 (PLMN-1) and the LAC-A, the mobile terminal moves to a different cell and the cell IND is received with the PLMN-1 and the LAI-B. In such case, the mobile terminal initiates the LAU procedure and sends the LAU request to the communication network. The communication network sends the LAU accept message with different LAI value. The different LAI value includes the PLMN-2 along with the LAC-C. When the mobile terminal receives the LAU accept message, the mobile terminal updates the LAI value (e.g., LAI-A) of the SIM with the received LAI value (e.g., LAC-C), and the mobile terminal will remove the PLMN-2 from the forbidden list if the PLMN-2 is present in the forbidden PLMN list. Further, the RR connection is released and the mobile terminal enters the idle mode. If the mobile terminal enters the different cell which is under the PLMN-2, and attempts the LAU procedure on the forbidden cell, the mobile terminal removes the forbidden PLMN from the forbidden PLMN list. When the mobile terminal attempts registration on the forbidden PLMN's, the mobile terminal receives the reject from the cell.
Consider yet another situation where the mobile terminal is registered with the PLMN 1 along with the LAC-A, the communication network sends the PLMN-2 along with the LAC-B in the LAU accept message, and the mobile terminal updates a Registered Public Land Mobile Network (RPLMN) value as PLMN-2 in the SIM. If the mobile terminal is restarted in a power ON mode, then the mobile terminal attempts to register with the PLMN-2 directly even though it is not part of the RPLMN. Further, the location area update procedure will be triggered on the PLMN-2. If the mobile terminal attempts the power ON registration on different PLMN-2, which does not accept the mobile terminal, then the communication network sends a reject message during the registration process.
Considering a situation including dual SIMs where the LAU procedure is repeatedly performed by a first SIM in response to detecting identities mismatch with respect to the LAI value received in the broadcasted system information and a LAI value received in the LAU accept message from the communication network. Then, the second SIM (i.e. SIM2) will not get a chance to perform registration procedure. This can cause the SIM 2 to be in no service condition. Thus, the Mobile Originating (MO) and/or a Mobile Terminating (MT) call to/from the SIM 2 fails.